Disposable blood dialyser unit

ABSTRACT

The invention concerns an improved dialyser unit of flat rectangular construction, comprising a flat membrane envelope provided with a blood inlet at one end and a blood outlet at the other end, membrane support material covering the two outer surfaces of the membrane envelope and being made up of an inner series of coplanar parallel strands against the outer surfaces of the membrane envelope and an outer series of coplanar parallel strands crossing the inner series of the side outwardly of the membrane envelope, spacer elements arranged across the free outer series of coplanar parallel strands of the membrane support material, and a housing having a dialysate inlet and outlet, defining a dialysate flow passage with the spacer elements and outer surfaces of the membrane envelope, the inner series of coplanar parallel strands of the membrane support material against the one outer surface of the membrane envelope being arranged at an angle relative to the inner series of coplanar parallel strands against the other outer surface of the membrane envelope.

May 1, 1973 llnited States Patent 91 Veronesi [54] DISPOSABLE BLOODDIALYSER UNIT Primary Examiner-Frank A. Spear, Jr. Att0rneyGerald D.Sharkin et a1.

ABSTRACT Italy [57] The invention concerns an improved dial [22] Filed:July 1, 1971 yser unit of at rectangular construction, comprising a flatmemfl brane envelope provided with a blood inlet at one end and a bloodoutlet at the other end,

[21] Appl. No.: 158,730

membrane sup- Related U.S. Application Data port material covering thetwo outer surfaces of the membrane envelope and being made up of aninner March 17,

series of coplanar parallel strands against the outer surfaces of themembrane envelope and an outer series of coplanar parallel strandscrossing the inner series 0 Foreign Application Priority Data f the sideoutwardly of the membrane envelope,

Mar. 27, 1969 Italy................................31044 A/69 spacerelements arranged across the free outer series of coplanar parallelstrands of the membrane support material outlet,

, and a housing having a dialysate inlet and defining a dialysate flowpassage with the spacer elements and outer surfaces of the membraneenvelope, the inner series of coplanar parallel strands of the membranesupport material against the one outer surface of the membrane envelopebein L 0 m U1 1]] 2 00 555 [[l Field of Search.......................

[56] References Cited UNITED STATES PATENTS ranged at an angle relativeto the Inner series of coplanar parallel strands against the other outersurface of the membrane envelope.

Xum 2 2 3 3 l 020 1 l 2 m2 3/1971 Nose 8/1970 Lavender et al.. 3,342,3289/1967 Swenson...........

1/1970 Ross et a].

1 Claim, 5 Drawing Figures PATENTEWY Hm v I 3, 730,351

' SHEET 3 OF 4 FIG. 3

INVENTOR:

Mario Nino Veronesi 2, ATTORNEY PATENTEU HAY U75 sum u or a m wE aw. n2w Q7 3 INVENTOR: Mario Nino Veropesi. By flf Q ATTORNEY This is acontinuation in part of copending application Ser. No. 20,305 filed onMar. 17, 1970, now abandoned.

The invention relates to an improved blood dialyser unit of therectangular Kiil type. More particularly, the invention concerns adialyser unit of the type comprising a membrane envelope through whichblood may be passed, netting structures to each side of the membraneenvelope to support the surfaces of the membrane envelope, and a housingenclosing the membrane envelope and netting structures and definingdialysate flow passages with the membrane envelope. Several dialyserunits of this type are known. Thus, for example, there is described inU.S. Pat. No. 3,448,690, a dialyser unit employing netting supportstructures adjacent a membrane envelope. Preparation of a haemodialysercan be a time-com suming operation, particularly where the dialyser unititself needs to be dismantled, cleaned, sterilised and thenreconstructed. Also, many dialyser units can suffer from a series ofdefects following on repeated use. It is one object of this invention toprovide a dialyser unit of the type described which is of low cost andsimple construction which may be disposed of after use.

Careful priming of the dialyser unit normally needs to be effected toeliminate all air contained in the unit. To ensure that no air isentrained in blood returned to the body from the dialyser unit, thehaemodialyser assembly is generally provided with an air trap, orsocalled debubbler. The flat rectangular dialyser unit of the type herecontemplated is generally clamped between two rigid clamp plates so thatthe unit is prevented from bulging and will retain its flat conditionwhile dialysate and blood are being passed through the dialyser unit. insome constructions, an inflatable shim is provided between the plates sothat the clamping force for maintaining the dialyser unit in flatcondition is not localised at a point (which may cause damage to thedialyser unit) but is spread over and against one flat surface of thedialyser unit to provide an even pressure. ln priming the dialyser unitwith blood it is conventional to tilt the clamp plates and hence thedialyser unit about a horizontal axis so that the blood inlet leading tothe membrane envelope is at a lower lever below the blood outlet leadingfrom the membrane envelope. This tilting operation is carried out in anendeavour to expel air wijhin the membrane envelope by filling this withblood from the lower level so that the air will be expelled through theoutlet as the leading face of the blood moves upwardly towards theoutlet during priming. It is an object of this invention to provide aconstruction in which the likelihood of entrapping air in the membraneenvelope during priming is reduced.

It is recognised in the field of blood dialysis that it is of advantagethat the blood flowing through the-membrane envelope be spread in a thinlayer in order to the membrane envelope not be great since otherwise ablood pump is required during the haemodialysis operation. For reasonssimilar to the fact that turbulent blood flow is desirable, it is alsodesirable that dialysate flow adjacent the membrane surfaces beturbulent. The dialyser unit of the present invention meets theserequirements particularly simply and effectively, as will more readilybe understood from the following description.

In accordance with the invention, there is provided a disposable blooddialyser unit of flat rectangular construction, comprising a flatmembrane envelope proachieve efficient dialysis. Also, localisedchannelling of the blood should as far as possible be avoided. Further,since laminar flow of blood can result in only the outer laminates ofblood being subjected to dialysis, it is desirable that blood flowthrough the membrane envelope be turbulent. At the same time, it isadvantageous that the resistance to flow of blood through vided with ablood inlet at one end and a blood outlet at the other end, membranesupport material covering the two outer surfaces of the membraneenvelopw and being made up of an inner series of coplanar parallelstrands against the outer surfaces of the membrane envelope and an outerseries of coplanar parallel strands crossing the inner series on theside outwardly of the membrane envelope, spacer elements arranged acrossthe free outer series of envelope parallel strands of the membranesupport material, and a housing having a dialysate inlet and outlet,defining a dialysate flow passage with the spacer elements and outersurfaces of the membrane envelope, the inner series of coplanar parallelstrands of the membrane support material against the one outer surfaceof the membrane envelope being arranged at an angle relative to theinner series of coplanar parallel strands against the other outersurface of the membrane envelope.

The flat membrane envelope may conveniently be made up from twosubstantially rectangular sheets of membrane material superimposed onone another and sealed together inwardly of their edges. The blood inletand blood outlet can in this arrangement be sealed between the sheets sothat the one sheet is sealed onto the one side of the blood inlet andblood outlet and the other sheet is sealed onto the other side of saidinlet and outlet. The inlet and outlets are thus conveniently of flattongue-like form.

The membrane support material covering the membrane envelope may also bein the form of two rectangular sheets. The nature and function of themembrane support material in the dialyser unit of the invention will bemost readily understood from the later description herein, withreference to the accompanying drawings. However, the support materialpreferably constitutes a plastic net structure made up of a first seriesof coplanar parallel plastic strands and a second series of coplanarparallel plastic strands bonded across and to each of said first series.Such bonded structure has the advantage that the strands making up thesup port material cannot be displaced relative to one another. Ofparticular importance is that the membrane support material covering thetwo outer surfaces of the membrane envelope can be pressed together bythe clamping action of clamp plates acting on the housing, withoutimpeding flow of blood through the membrane envelope. In general, it haspreviously been necessary to provide spacer elements between membranesupports so that the membrane envelope is free to part and so define apassage for blood flow. Additionally, or sometimes alternatively,elements have been arranged against the surfaces of the membraneenvelope in staggered relationship so as to deform the membrane profileto cause turbulence in the blood as it flows through the envelope. Themembrane support material employed in the dialyser unit of the presentinvention results in the membrane envelope taking up a profile whichcreates a particularly efficient type of turbulence in the blood.

Apart from creating a state of turbulence in the blood, it is desirablethat turbulence exist in the dialysate. A certain degree of turbulencein the dialysate occurs in most constructions by virtue of the irregularprofile of the membrane envelope during use. In the dialyser unit of thepresent invention, the two inner series of coplanar parallel strands ofmembrane support material against the two outer surfaces of the membraneenvelope will, in effect, be embedded in the membrane envelope by virtueof bulging of the membrane envelope between the strands during use. Theouter two series of coplanar parallel strands crossing the said twoinner series of strands will however effectively be within the dialysateflow passage defined by the housing and spacer elements and outersurfaces of the membrane envelope. The outer series of strands are inclose proximity of the outer surfaces of the membrane envelope and serveto create desirable additional turbulence in the dialysate immediatelyadjacent the outer surfaces of the membrane envelope.

As has already been indicated, the inner series of coplanar parallelstrands of the membrane support V material against the one outer surfaceof the membrane envelope are arranged at an angle relative to the innerseries of coplanar patallel strands against the other outer surface ofthe membrane envelope. It will be readily appreciated that the oneseries of strands will, during use of the dialyser unit, result in theone surface of the membrane envelope taking up a channelled profileseries between and along the length of the series of strands againstsaid surface, and the other surface of the membrane envelope taking up asimilar channelled profile series along the length of the series ofstrands against said other surface at angle to the first mentionedchannelled profile. Where the membrane support material covering thesurfaces of the membrane envelope is held close together, for example byclamp plates acting on the housing, the membrane envelope will define across-channel system with the peaks of the channels touching at pointswhere the series of strands against the one outer surface of themembrane support envelope cross the series of strands arranged at anangle against the other outer surface of the membrane envelope.

The channelled profile series taken up by the mem' brane envelope willnaturally influence the nature and direction of blood flow through themembrane envelope. Thus, the one channelled profile series will inclineblood flow along the length of its series of channels, while the otherchannelled profile series will in turn incline blood flow along itsseries of channels at an angle to the first mentioned series ofchannels. As a first consideration, in order to obtain a consistentdegree of dialysis, it is desirable that blood flow not be inclined toany particular region within the membrane envelope. This point, togetherwith other desirable characteristics, is effectively achieved byarranging the series of coplanar parallel strands against the one outersurface of the membrane envelope at a determined acute angle to one sideof the overall direction of blood flow in the membrane envelope, i.e.,at a determined angle to one side of the longitudinal axis of the flatrectangular blood dialyser unit here contemplated, and arranging theseries of coplanar strands against the other outer surface of themembrane envelope at the same determined acute angle to the other sideof the overall direction of blood flow. It has been indicated that anobject of the invention is to provide a construction in which thelikelihood of entrapping air in the membrane envelope during priming isreduced. The arrangement of the series of coplanar strands at saiddetermined acute angles results in blood flow in the membrane envelopebeing inclined to one side of the overall direction of blood flow by theone series of coplanar strands and to the other side of the overalldirection of blood flow by the other series of coplanar strands. Thus, aspreading action takes place on blood feeding into the membraneenvelope, which in priming results in the formation of a substantiallylinear leading face of blood normal to the overall direction of bloodflow. The formaton of said linear leading face can be employed toadvantage in expelling air which may be contained in the membraneenvelope particularly in a construction where said leading face can bemade to extend across the entire width of the membrane envelope from thetime of entry of blood into the effective dialysis area of the membraneenvelope. In order to achieve this function, a blood distributionchannel extending across the width of the dialyser unit may be providedat the inlet end of the dialyser unit. The distribution channel mayconveniently comprise a marginal region of the membrane envelope whichis capable of bulging or diverging outwardly away from the seal todefine a wedge-sectioned distribution channel. This function may beachieved by leaving a marginal region of the membrane envelopesuncovered by the support material or by flattening the support materialso that the membrane envelope is free to part at said marginal region.One or more blood inlets leading into the envelope, i.e., in thisconstruction into the marginal region may be provided.

The outlet end of the dialyser unit can similarly be provided with ablood collection channel so that blood having passed through themembrane envelope can collect and pass through the outlet from themembrane envelope. Conveniently, the arrangement of the blooddistribution channel and inlet and blood collection channel and outletare identical so that blood may be passed through the envelope in eitherdirection. The one or more blood inlets and outlets may convenientlyhave openings flared outwardly along the width of the membrane envelopeto encourage distribution of blood along the distribution channel. Thespacer elements against the free outer series of coplanar parallelstrands of the membrane essentially serve the function of providing adialysate flow passage between the inner surfaces of the housing and themembrane envelope. The spacer elements conveniently form part of thehousing itself, which may comprise a pair of rectangular plasticmouldings with suitable spacer elements provided on the inner surfaces.The spacer elements may, for example, be defined by longitudinallyarranged corrugations, which additionally serve to strengthen theoverall construction of the dialyser unit.

The housing, which is provided with a dialysate inlet and outlet,defines the dialysate flow passage-with the spacer elements and outersurfaces of the membrane envelope. As mentioned, the housing maycomprise a pair of rectangular plastic mouldings. These mouldings mayconventiently be provided with flat marginal areas about the mouldingswhere they may be sealed together with the spacer elements (which mayform part of the housing), membrane support material and membraneenvelope between them. A seal, e.g., of rubber, may furthermore beprovided inwardly of said flat marginal region, between which sheets ofmembrane material which may make up the membrane envelope may be sealed.inwardly of the seal, the housing mouldings may conveniently be providedwith a shoulder, which along the longitudinal length is approximatelycoplanar with the flat marginal regions, between which a correspondinglynarrow marginal region of the membrane support material will be clampedupon sealing the mouldings together. In this fashion, the membranesupport material can be held in position within the dialyser unit.

The housing mouldings may be moulded to define dialysate distributionand collection channels at the inlet and outlet ends of the dialyserunit. These channels assist in achieving homogeneous flow of dialysateover the membrane envelope and to reduce formation of high and lowpressure zones in the dialysate as it enters and leaves the dialyserunit.

An embodiment of a dialyser unit in accordance with the invention willnow be described with reference to the accompanying drawings, in which:

FIG. 1 shows a view in perspective of an assembled dialyser unit;

FIG. 2 shows another view of the dialyser unit of FIG. 1 which is partcut-away to show the inside of the unit;

FIG. 3 shows an exploded perspective view in detail of membrane envelopeand membrane support material within the dialyser units shown in FIGS. 1and 2;

FIG. 3 shows a part perspective view and part crosssection taken at AAof FIG. 2;

FIG. 5 shows a part perspective view and part crosssection taken at 8-3of FIG. 2.

Referring in combination to FIGS. 1 and 2, the flat rectangular dialyserunit comprises a flat membrane envelope made up from two rectangularsheets 110a and Nb of membrane material, two sheets of membrane supportmaterial 12a and 12b covering the membrane envelope, spacer elementscomprising two series of corrugations 14a and 14b, and a housingcomprising a pair of rectangular plastic moulding 16a and 16b.

The membrane envelope has a blood inlet 18 and a blood outlet 20, andeach of the plastic mouldings 16a and 16b carries a dialysate inlet 22and dialysate outlet 24. These inlets and outlets are identical and theconstruction is such that inlets and outlets are reversible.

As can best be seen from detailed FIG. 3, each of the two sheets 12a and12b of membrane support material are made up of an inner series ofcoplanar parallel strands 26a and 26b respectively and an outer seriesof coplanar parallel strands 23a and 28b crossing said inner series onthe side outwardly of the sheets of membrane material a and 10b. In theassembled or unexploded situation, the inner series of coplanar parallelstrands 26a would be against the outer surface 301: of

the sheet ofmembrane material 1012. As will be seen from the FIG. 3, theinner series of strands 26a and 26b are at an angle to one another. Notshown in detailed FIG. 3, but as will be clear from FIGS. 2, d and 5,the spacer elements comprising the two series of corrugations Ma and Nbwill in the assembled situation of FIG. 3 be situated across the freeouter series of coplanar parallel strands 28a and 28 b.

Overall blood flow direction (which corresponds in direction to thelongitudinal axis of the rectangular dialyser) is in the FIGS. 11, 2,and 3 indicated by arrows 32. As can be seen from FIGS. 2 and 3 the oneinner series of coplanar parallel strands 26a is arranged at an acuteangle 33a to one side of the overall blood flow direction and the otherinner series of coplanar parallel strands 26b is arranged at the sameangle 33b to the other side of the overall blood flow direction.

Referring particularly to F IGS. 2 and 5, the rectangular p asticmouldings 16a and 16b making up the housing are provided with flatmarginal areas 341 about the mouldings where they may be sealedtogether, e.g., by heat or solvent sealing. A seal 36 located in a notch38 is provided inwardly of the marginal region. The sheets of membranematerial 10a and 10b are sealed together along the seal 36 inwardly oftheir edges to form the membrane envelope. Inwardly of the seal 36, thehousing mouldings are provided with shoulders 40, between which narrowmarginal regions of the two sheets of membrane support material 12c and12b are clamped and thus held in position within the dialyser unit.

Referring particularly to FIG. 4, the inlet end is provided with a blooddistribution channel (not shown) but which exists between the seal 36and the shoulder 40 along the width of the dialyser unit. The bloodinlet 13 is of flat tongue-like construction and has a mouth 42 which,is flared outwardly along the width of the membrane envelope, i.e.,along the length of the distribution channel. The blood inlet is sealedbetween the sheets Ella and lltlb of membrane material. It will beappreciated from FIGS. ll, 2 and 4 that the distribution channel existsin the region 44 since the sheets of membrane support material 12a and12b stop short of the seal 36. Unlike the arrangement along thelongitudinal edges shown in the cut-away section of FIG. 2, there existsalong the width of the dialyser unit a space between the seal 36 and theshoulder 40 within which the membrane envelope can diverge or bulgeoutwardly away from the seal and thus define the distribution channel.

The housing mouldings 16a and 16b are at each end moulded to definedialysate distribution and collection channels 46 and 48.

In priming the dialyser unit, blood passes through the flared mouth 42of the inlet 18 into the-membrane envelope to first form a line of bloodat the seal along the distribution channel in the region 44. Air whichis in the distribution channel, e.g., that which has flowed in from theinlet should normally be located ahead of the leading face of the floodsince priming is effected with the inlet end at a lower level. When theblood moves upwardly from the lower distribution channel and between thesheets of membrane support material and 12b, a spreading action takesplace on the blood, which by virtue of the arrangement of strands 26aand 28a and 28b of the membrane support materials.

What is claimed is:

1. A disposable blood dialyser unit of flat rectangular construction,comprising a flat membrane envelope provided with a blood inlet at oneend and a blood outlet at the other end, membrane support materialcovering the two outer surfaces of the membrane envelope and being madeup of an inner series of coplanar parallel strands against the outersurfaces of the membrane envelope and the outer series of coplanarparallel strands crossing the inner series on the side outwardly of themembrane envelope, spacer elements arranged across the free outer seriesof coplanar parallel strands of the membrane support material, and ahousing having a dialysate inlet and outlet, defining a dialysate flowpassage with the spacer elements and outer surfaces of the membraneenvelope, the inner series of coplanar parallel strands of the membranesupport material against the one outer surface of the membrane envelopebeing arranged at a determined acute angle to one side of the overallblood flow direction through the membrane envelope and the other seriesof coplanar parallel strands being arranged at the same determined acuteangle to the other side of the overall blood flow direction.

1. A disposable blood dialyser unit of flat rectangular construction,comprising a flat membrane envelope provided with a blood inlet at oneend and a blood outlet at the other end, membrane support materialcovering the two outer surfaces of the membrane envelope and being madeup of an inner series of coplanar parallel strands against the outersurfaces of the membrane envelope and the outer series of coplanarparallel strands crossing the inner series on the side outwardly of themembrane envelope, spacer elements arranged across the free outer seriesof coplanar parallel strands of the membrane support material, and ahousing having a dialysate inlet and outlet, defining a dialysate flowpassage with the spacer elements and outer surfaces of the membraneenvelope, the inner series of coplanar parallel strands of the membranesupport material against the one outer surface of the membrane envelopebeing arranged at a determined acute angle to one side of the overallblood flow direction through the membrane envelope and the other seriesof coplanar pArallel strands being arranged at the same determined acuteangle to the other side of the overall blood flow direction.